Fire officials have come up empty in their search for a cause for the September fire that led to the deaths of 14 residents at a Nashville nursing home. They have officially closed the investigation, saying they may never know the real reason for the fire, which set off nationwide scrutiny of safety policies.

At one time, an electric bed and strip outlet were suspected, but testing of them did not yield positive results. Flames destroyed many other items that might have helped explain the blaze. As a result, the cause will be listed as undetermined yet unintentional, officials said.

The fire has sparked a variety of civil lawsuits against the facility’s owners. The building did not have automated sprinklers but was in compliance with state law at the time.